Suspension assembly, head suspension assembly and disk device with the same

ABSTRACT

According to one embodiment, a suspension assembly includes a support plate, a trace member on the support plate and a drive element mounted on the trace member. The trace member includes a metal plate, and a multilayered member on the metal plate. The multilayered member includes a first insulating layer, a conductive layer stacked on the first insulating layer, a second insulating layer stacked on the conductive layer. The multilayered member includes a mount portion on which the drive element is mounted, and a branching portion arranged along the mount portion with a gap therebetween. At least one portion of the branching portion is formed into a thin portion having a thickness less than other portions of the multilayered member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 15/374,276filed Dec. 9, 2016, which is a continuation of application Ser. No.14/741,649 filed Jun. 17, 2015 and is based upon and claims the benefitof priority from Japanese Patent Application No. 2015-049807, filed Mar.12, 2015, the entire contents of each are incorporated herein byreference.

FIELD

Embodiments described herein relate generally to a suspension assembly,a head suspension assembly and a disk device with the same.

BACKGROUND

In recent years, disk devices such as magnetic disk devices and opticaldisc devices are widely used as external storage devices for computersand image recorders.

As a disk device, for example, the magnetic disk device generallyincludes a magnetic disk provided in a base, a spindle motor configuredto support and rotate the magnetic disk and a suspension assemblyconfigured to support a magnetic head. The suspension assembly includesa suspension attached to a distal end portion of an arm, a trace member(flexure, wiring trace) disposed on the suspension, and a load beam. Themagnetic head is supported on a gimbal portion of the trace member, thusforming a head suspension assembly.

In recent years, such a suspension assembly has been proposed, in whicha piezoelectric element (PZT element) as a drive element is mounted inthe vicinity of the gimbal portion of the trace member, and thus themagnetic head is minutely displaced in a seek direction byexpansion/contraction of the piezoelectric element. According to thissuspension assembly, it is possible to finely control the movement ofthe magnetic head by controlling the voltage supplied to thepiezoelectric element.

In the suspension assembly such as above, when the piezoelectric elementexpands or contracts by voltage application, the piezoelectric elementmay curve in the thickness direction. In this case, part of expansion orcontraction of the piezoelectric element escapes in the curvingdirection of the piezoelectric element and the displacement (stroke) ofthe magnetic head decreases. For this reason, it becomes difficult tocontrol the displacement of the magnetic head in line with thedisplacement of the piezoelectric element.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view showing a hard disk drive (HDD) accordingto a first embodiment;

FIG. 2 is a side view showing a magnetic head and a suspension of a headsuspension assembly, and a magnetic disk in the HDD;

FIG. 3 is a plan view of the head suspension assembly;

FIG. 4 is a perspective view of the head suspension assembly;

FIG. 5 is an exploded perspective view showing the magnetic head, apiezoelectric element, a wring member and a load beam of the suspensionassembly;

FIG. 6 is a plan view of a distal end portion of the suspensionassembly;

FIG. 7A is a longitudinal sectional view of a branching portion (bridgeportion) of the trace member taken along line A-A in FIG. 6;

FIG. 7B is a cross sectional view of a thin part of the branchingportion of the trace member taken along line B-B in FIG. 6;

FIG. 7C is a cross sectional view of a non-thin part of the branchingportion taken along line C-C in FIG. 6;

FIG. 8 is a diagram showing strokes obtained by expansion/contraction ofa drive element for various types of trace members in comparison;

FIG. 9 is a cross sectional view of a thin part of a trace member in asuspension assembly according to a second embodiment;

FIG. 10 is a cross sectional view of a thin part of a trace member in asuspension assembly according to a third embodiment;

FIG. 11 is a cross sectional view of a thin part of a trace member in asuspension assembly according to a fourth embodiment; and

FIG. 12 is a cross sectional view of a thin part of a trace member in asuspension assembly according to a fifth embodiment.

DETAILED DESCRIPTION

Various embodiments will be described hereinafter with reference to theaccompanying drawings. In general, according to one embodiment, asuspension assembly comprises a support plate; a trace member providedon the support plate; and an expandable/contractable drive elementmounted on the trace member. The trace member comprises a metal plateincluding an end portion fixed to the support plate, and a multilayeredmember on the metal plate. The multilayered member comprises a firstinsulating layer, a conductive layer stacked on the first insulatinglayer, and a second insulating layer stacked on the conductive layer.The multilayered member includes a mount portion on which the driveelement is mounted, and a branching portion arranged along the mountportion with a gap therebetween. The branching portion comprises atleast one portion formed into a thin portion having a thickness lessthan other portions of the multilayered member.

Hereafter, as disk devices, hard disk drives (HDD) according toembodiments will now be described in detail.

First Embodiment

FIG. 1 shows an internal structure of an HDD when a top cover isremoved. As shown in FIG. 1, the HDD includes a housing 10. The housing10 includes a base 12 of a rectangle box shape with an upper surfaceopened, and a top cover (not shown) configured to cover the upper endopening of the base 12. The base 12 includes a bottom wall 12 a ofrectangular shape and sidewalls 12 b set to rise along the side edges ofthe bottom wall 12 a.

The housing 10 accommodates therein two magnetic disks 16 as recordingmedia, and a spindle motor 18 as a drive section configured to supportand rotate the magnetic disks 16. The spindle motor 18 is provided onthe bottom wall 12 a. The magnetic disks 16 are fitted coaxially on ahub (not shown) of the spindle motor 18, and clamped with a clamp spring27, thus fixed to the hub. The magnetic disks 16 are supported parallelto the bottom wall 12 a of the base 12. The magnetic disks 16 arerotated by the spindle motor 18 in a direction of arrow A at aparticular speed.

The housing 10 accommodates therein a plurality of magnetic heads 17configured to write and read data to and from the magnetic disks 16, anda head stack assembly (referred to as HSA hereafter) 22 configured tosupport these magnetic heads 17 so as to be movable with respect to themagnetic disks 16.

Further, the housing 10 accommodate a voice coil motor (referred to asVCM hereafter) 24 configured to rotate and position the HSA 22, a rampedloading mechanism 25 configured to hold the magnetic head 17 at anunloading position away from the respective magnetic disk 16 when themagnetic head 17 is moved to the outermost periphery of the magneticdisk 16, a latch mechanism 26 configured to hold the HSA 22 in anevacuation position when a shock or the like acts on the HDD, and asubstrate unit 21 including a conversion connector, etc.

Onto an outer surface of the bottom wall 12 a of the base 12, a printedcircuit board (not shown) is fixed by screws. The printed circuit boardis configured to control the operations of the VCM 24 and the magneticheads 17 through the substrate unit 21, and control the spindle motor18. In the sidewall 12 b of the base 12, a circulation filter 23 isprovided to capture the dust generated in the housing 12 by operation ofmovable members, to be located in the outside of the magnetic disks 16.The sidewall 12 b is provided with a respiratory filter 15 configured tocapture dust from the air flowing into the housing 10.

As shown in FIG. 1, the HSA 22 comprising a rotatable bearing unit 28,four arms 32 attached to the bearing unit 28 in a stacking state, asuspension assembly 30 extending from each of the arms 32 and spacerrings (not shown) arranged to stack between the arms 32, respectively.Each arm 32 is formed of, for example, stainless steel or aluminum intothe shape of a slim plate. Each arm 32 includes a distal end portion onan extending end side, and the distal end portion includes a bearingsurface with holes for caulking (not shown), formed therein.

The HSA 22 comprises a support frame extending in a direction oppositeto the arms 32 from the bearing unit 28, and a voice coil, which is apart of the VCM 24, is embedded in the support frame. The voice coil islocated between a pair of yokes 37 mounted on the base 12 andconstitutes the VCM 24 together with these yokes 37 and a magnet (notshown) fixed to one of the yokes 37.

As shown in FIG. 1, the substrate unit 21 comprises a main substrate 21a and a relay flexible printed circuit board (FPC) 21 b extending outfrom the main substrate 21 a of the unit. An extending end of the relayFPC 21 b constitutes a connection end portion and is being fixed to thevicinity of the bearing unit 28 of the HSA 22. A connection end 40 c(FIG. 3) of a flexure (trace member) 40 of each suspension assembly 30,which will be described later, is mechanically and electricallyconnected to the connection end portion of the relay FPC 21 b. With thisstructure, the substrate unit 21 is electrically connected to themagnetic head 17 and a drive element through the relay FPC 21 b and theflexure 40.

FIG. 2 schematically shows a magnetic head in a flying state and themagnetic disk. As shown in FIGS. 1 and 2, the magnetic disk 16 comprisesa substrate 101 of, for example, a nonmagnetic material formed into adisk having a diameter of about 2.5 inches (6.35 cm). On both surfacesof the substrate 101, a soft magnetism layer 102 of a materialexhibiting soft magnetic characteristics is formed as an underlyinglayer, a magnetic recording layer 103 is formed thereon and a protectivefilm layer 104 is formed thereon in this order while stacking one onanother.

As shown in FIG. 2, the magnetic head 17 is formed as a flying-type headand comprises a slider 31 formed into a substantially rectangularparallelepiped shape and a head portion 33 formed in an end portion onthe (trailing) side of an outflow end of the slider 31. The magnetichead 17 is supported on the distal end portion of the suspension 34through a gimbal portion 36 of the flexure, which will be describedlater. The magnetic head 17 flies by air flow B produced between thesurface of the magnetic disk 16 and the slider 31 by rotation of themagnetic disk 16. The direction of the air flow B coincides with thedirection of rotation A of the magnetic disk 16. The slider 31 isarranged so that the longitudinal direction of the slider 31substantially coincides with the direction of the air flow B withrespect to the surface of the magnetic disk 16.

Next, the structure of the suspension assembly 30 will now be describedin detail. FIG. 3 is a plan view of the suspension assembly and FIG. 4is a perspective diagram of the suspension assembly.

As shown in FIGS. 1, 3 and 4, the suspension assembly 30 comprises asuspension 34 extending out from the respective arm 32, and therespective magnetic head 17 is attached to the distal end portion ofthis suspension 34. Note that a set of a magnetic head 17 and asuspension assembly 30 supporting the magnetic head as a unit is calleda head suspension assembly.

The suspension 34 which functions as a support plate comprises arectangular base plate 42 of a metal plate having a thickness of severalhundred micrometers and a load beam 35 having an elongated plate springform of a metal plate having a thickness of several tens of micrometers.The load beam 35 is fixed to the base plate 42 as a proximal end portionis overlaid on the distal end portion of the base plate 42 and they arewelding together by a plurality of locations. The width of the proximalend portion of the load beam 35 is formed substantially equally to thewidth of the base plate 42. At the distal end of the load beam 35, aslim rod-shaped tab 46 is provided to protrude therefrom.

The base plate 42 comprises a circular opening 42 a provided at theproximal end portion thereof, an annular projection 43 located along thecircumference of the opening 42 a. The base plate 42 is jointed to thedistal end portion of the arm 32 by fitting the projection 43 into acircular hole for calking (not shown) formed in the bearing surface ofthe arm 32, and caulking the projection 43. The proximal end of the baseplate 42 may be fixed to the distal end of the arm 32 by laser welding,spot welding or adhesion.

The suspension assembly 30 comprises a pair of piezoelectric elements(PZT elements) 50, and an elongate belt-shaped flexure (trace member) 40configured to transmit recording and reading signals and drive signalsof the piezoelectric element 50. As shown in FIGS. 3 and 4, the flexure40 extends along a side edge of the arm 32 as the distal end portion 40a is attached on the load beam 35 and the base plate 42 and the latterhalf (extending portion) 40 b extends out from the side edge of the baseplate 42. The connection end 40 c located at the tip of the extendingportion 40 b comprises a plurality of contact pads 40 f and the contactpads 40 f are connected to the aforementioned relay FPC 21 b.

The distal end portion of the flexure 40 is located above the distal endportion of the load beam 35 and forms the gimbal portion 36 whichfunctions as an elastic support member. The magnetic head 17 is placedand fixed on the gimbal portion 36, and is supported by the load beam 35through the gimbal portion 36. A pair of piezoelectric elements 50 asdrive elements are attached to the gimbal portion 36 and are located inthe proximal end side of the load beam 35 with respect to the magnetichead 17.

FIG. 5 is an exploded perspective view of the piezoelectric element,flexure, load beam and magnetic head of the suspension assembly, andFIG. 6 is an enlarged plan view showing a distal end portion of thesuspension assembly.

As shown in FIGS. 3 to 6, the flexure 40 comprises a thin metal plate(metal plate) 44 a of stainless steel or the like, used as a base, and abelt-shaped multilayered member 41 attached or adhered to the thin metalplate 44 a, which are shaped into a slim multilayer plate.

The multilayered member 41 comprises a base insulating layer (firstinsulating layer) 44 b, most of which is fixed to the thin metal plate44 a, a conductive layer (trace pattern) 44 c formed on the baseinsulating layer 44 b and comprising a plurality of signal trace lines45 a and drive trace lines 45 b and a cover insulating layer (secondinsulating layer) 44 d (FIG. 7A and FIG. 7B) stacking on the baseinsulating layer 44 b so as to cover the conductive layer 44 c. Thedistal end portion 40 a of the flexure 40 is attached, with its thinmetal plate 44 a side, to the surfaces of the load beam 35 and the baseplate 42, or welded thereto by spot welding by a plurality of weldingpoints.

In the gimbal portion 36 of the flexure 40, the thin metal plate 44 acomprises a rectangular tongue portion (support portion) 36 a located inan proximal end side thereof, a substantially rectangular proximal endportion (proximal end plate member) 36 b located in a proximal end sidewhile sandwiching the tongue portion 36 a and a space 36 e, a pair ofslim outriggers (link portion) 36 c extending from the tongue portion 36a to the proximal end portion 36 b, a pair of island-shaped separatingplates 36 d provided in the space 36 e between the tongue portion 36 aand the proximal end portion 36 b and a pair of handles (supportingprojections) 36 f projecting from both side edges of the tongue portions36 to the both sides.

The proximal end portion 36 b is attached or fixed by spot welding onthe surface of the load beam 35. The tongue portion 36 a is formed tohave a size and shape on which the magnetic head 17 can be mounted, forexample, into a substantially rectangular shape. The tongue portion 36 ais arranged so that the central axis thereof in its width directioncoincides with the central axis C of the suspension 34. Further, thetongue portion 36 a is arranged so that the substantially centralportion thereof contacts a dimple (projecting portion) 48 provided in adistal end portion of the load beam 35. Furthermore, the tongue portion36 a can be displaced in various directions when the pair of outriggers36 c elastically deform. With this structure, the tongue portion 36 aand the magnetic head 17 mounted on the tongue portion 36 a are able toflexibly follow surface fluctuation of the magnetic disk 16 in rollingand pitching directions, thereby making it possible to maintain a narrowgap between the surface of the magnetic disk 16 and the magnetic head17. A pair of handles 36 f are formed of the thin metal plate 44 a to beintegrated with the tongue portion 36 a and project from both side-edgesof the tongue portion 36 a in directions which intersect substantiallyperpendicularly with the central axis C. The handles 36 f may be formedof, not only the thin metal plate 44 a itself, but also the conductivelayer 44 c, the base insulating layer 44 b or the cover insulating layer44 d stacked on the thin metal plate 44 a.

In the gimbal portion 36, a portion of the multilayered member 41 of theflexure 40 separates into two parts, which are located on both sides ofthe central axis C of the suspension 34. The multilayered member 41comprises a proximal end portion 47 a fixed on the proximal end portion36 b of the thin metal plate 44 a, a distal end portion 47 b attached onthe tongue portion 36 a, a pair of belt-shaped first bridge portions 47c extending from the proximal end portion 47 a to the distal end portion47 b above through the separation plates 36 d, and a pair of belt-shapedsecond bridge portions (branch portions) 47 d extending along with thefirst bridge portions 47 c from the proximal end portion 47 a to thehalfway point of the first bridge portions 47 c and emerging with thefirst bridge portions 47 c. Each of the first bridge portions 47 c formsa mounting portion on which the drive element, described later, is to bemounted. The first bridge portions 47 c are located on both respectivesides of the tongue portion 36 a along with the outriggers 36 c, andextend substantially parallel to the central axis C of the suspension34, that is, along the longitudinal direction of the load beam 35.Further, the first bridge portions 47 c extend through above the handles36 f and the crossbars of the outriggers 36 c, and are partially fixedthereto. Furthermore, the first bridge portions 47 c are arranged sothat the proximal end side portions, the distal end side portions andthe middle portions are located on the thin metal plate 44 a. Note thatthe outriggers 36 c may be provided between the tongue portion 36 a andthe first bridge portions 47 c, respectively, in which case, the firstbridge portions 47 c are partially fixed to the handles 36 f. The pairof island-shaped separation plates 36 d of the thin metal plate 44 a arefixed to the lower surfaces of the first bridge portions 47 c between amerging portion 47 f and the proximal end portion 47 a.

As shown in FIG. 6 and FIG. 7A, each of the second bridge portions 47 dis located between the respective first bridge portion 47 c and therespective outrigger 36 c, and extends along with these members. Each ofthe second bridge portions 47 d merges with the respective first bridgeportion 47 c in the merging portion 47 f in the vicinity of therespective handle 36 f. In the merging portion 47 f, the angle betweenthe first bridge portion 47 c and the second bridge portion 47 d is setto 45 degrees or greater but less than 90 degrees. As described, most ofthe second bridge portion 47 d is provided along the first bridgeportion 47 c with a gap therebetween except for the proximal end portionand the distal end portion. Further, the second bridge portions 47 d arelocated off the thin metal plate 44 a, and not provided on top of thethin metal plate 44 a.

In the gimbal portion 36, the conductive layer 44 c of the multilayeredmember 41 comprises a plurality of signal traces 45 a extending from theproximal end portion 47 a to the distal end portion 47 b through thesecond bridge portions 47 d, the merging portions 47 f and the firstbridge portions 47 c, and a plurality of drive traces 45 b extending tothe halfway point of the first bridge portions 47 c from the proximalend portion 47 a. The signal traces 45 a are connected to a plurality ofelectrode pads 40 d provided in the distal end portion 47 b. Note thatthe drive traces 45 b may be extended to the halfway point of the firstbridge portions 47 c from the proximal end portion 47 a through thesecond bridge portions 47 d and the merging portions 47 f.

As shown in FIG. 6, in the gimbal portion 36, the first bridge portions47 c, the second bridge portions 47 d, the signal traces 45 a, the drivetraces 45 b of the multilayered member 41 and the outriggers 36 c of thethin metal plate 44 a, described above, are located in both sides of thetongue portion 36 a, respectively, and are symmetrically formed withrespect to the central axis C of the suspension 34.

As shown in FIGS. 3 to 6, the magnetic head 17 is fixed to the tongueportion 36 a by adhesive. The magnetic head 17 is arranged so that thelongitudinal axis line thereof coincides with the central axis C of thesuspension 34, and also the substantially central portion of themagnetic head 17 is located above the dimple 48.

A recording/reading element of the magnetic head 17 is electricallyconnected to a plurality of electrode pads 40 d of the distal endportion 47 b with conductive adhesives such as solder or silver paste.Thus, the magnetic head 17 is connected to the signal traces 45 aconfigured to transmit recording and reading signals through theelectrode pads 40 d. Note that by forming the second bridge portions 47d branched from the first bridge portions 47 c and forming a pluralityof signal traces 45 a through the second bridge portions 47 d, thesignal traces 45 a can be routed while detouring around thepiezoelectric element 50.

A pair of piezoelectric elements 50, which function as drive elements,are, for example, thin-film piezoelectric elements (PZT elements) of arectangular plate shape. As the piezoelectric elements 50, not only athin-film type (about 10 μm in thickness) but a bulk type or bulklamination type (not less than 50 μm in thickness) may be used.Alternatively, not only PZT elements but other types of piezoelectricelements may be used as the piezoelectric elements 50. Further, as thedrive elements, not only piezoelectric elements but other types whichcan be expanded and contracted by application of current may be used.

As shown in FIGS. 3 to 6, the piezoelectric elements 50 are attached tothe upper surfaces of the first bridge portions 47 c, respectively, withadhesive, etc. In other words, each of the first bridge portions 47 cformed of the multilayered members 41 comprises a lower surface opposingthe thin metal plate 44 a and an upper surface located on an oppositeside to the lower surface, and a piezoelectric element 50 is attached tothe upper surface. The piezoelectric elements 50 are disposed so thatthe longitudinal directions thereof (expansion/contraction directions)are parallel to the longitudinal directions of the load beam 35 and thefirst bridge portions 47 c. The two piezoelectric elements 50 arearranged to be parallel to each other and also displaced to the proximalend portion 47 a side of the multilayered member 41 with respect to themagnetic head 17 on both sides of the magnetic head 17. Note that thepiezoelectric elements 50 may be arranged to incline towards thelongitudinal directions of the first bridge portions 47 c, and forexample, the two piezoelectric elements 50 may be arrange in crossingdirections such as a V-shape formation.

Each of the piezoelectric elements 50 is attached to the respectivefirst bridge portion 47 c in such a state that one of the longitudinal(expansion/contraction directions) end portions thereof overlaps theproximal end portion 36 b of the thin metal plate 44 a and the otheroverlaps the respective separation plate 36 d. Each of the piezoelectricelements 50 is electrically connected to the drive traces 45 bconfigured to transmit drive signals.

At least a part of each of the second bridge portions 47 d arrangedalong the first bridge portions 47 c with a gap therebetween, where therespective piezoelectric element 50 is mounted, is formed thinner thanthe rest of the multilayered member 41 (as to a total thickness of thefilms and layers) so as to form a thin portion 60. In this embodiment,for example, the longitudinal middle portion located by thepiezoelectric element 50 in each of the second bridge portions 47 d isformed into the thin portion 60 having a smaller thickness. The width ofthe thin portion 60 is the same as the width of the second bridgeportion 47 d. Note that not only partially, but the entire second bridgeportion 47 d may be formed thin. The location and length of the thinportion 60 formed in the second bridge portion 47 d may be set optimallyin consideration of the strength and rigidity of the multilayered themember 41 as a whole.

FIG. 7A is a longitudinal section of the second bridge portion 47 d,FIG. 7B is a cross section of the thin portion 60 and FIG. 7C is a crosssection of the other portion of the second bridge portion, which is notthinned (non-thinned portion). As shown in FIGS. 7A, 7B and 7C, the baseinsulating layer 44 b in the thin portion 60 is formed thinner than theother portion (non-thinned portion) of the base insulating layer 44 b ofthe multilayered member 41. For example, the thickness of the baseinsulating layer 44 b in the non-thinned portion is 8 μm, whereas thethickness of the base insulating layer 44 b in the thin portion 60 is 4μm, which is substantially a half. Note that the difference in thicknessbetween the base insulating layer 44 b in the non-thinned portion andthe thin portion 60 should desirably be 1 μm or more. Therefore, thethickness T1 of the thin portion 60 is set thinner than the thickness T2of the other portion (non-thinned portion) of the multilayered member 41by 1 μm or more.

The multilayered member 41 including the above-described thin portion 60can be formed in the following process. That is, for example, afterforming a base insulating layer, a photoresist is formed on the baseinsulating layer. The entire photoresist is exposed using a photomaskincluding a part corresponding to the thin portion, which has lighttransmissivity and other parts having a different light transmissivity,followed by development. Further, the base insulating layer is etchedwith the obtained photoresist. Thus, a base insulating layer including athin portion is formed. After that, a conductive layer and a coverinsulating layer are stacked on the base insulating layer, and thus themultilayered member 41 including the thin portion 60 is obtained.

In an HDD having the above-described structure, the piezoelectricelement 50 is expanded and contracted in the longitudinal directionsthereof (the longitudinal directions of the first bridge portion 47 c)when applying voltage (driving signal) to the piezoelectric element 50through the drive traces 45 b. As shown in FIG. 6 with an arrow E, thepair of first bridge portions 47 c strokes in opposite directions fromeach other by driving the two piezoelectric elements 50 in reversedirections with respect to each other when they expand and contract. Thefirst bridge portions 47 c rock the tongue portion 36 a and the magnetichead 17 of the gimbal portion 36 in the directions indicated by an arrowD around the dimple 48 via the handles 36 f. Thus, the magnetic head 17can be displaced by the expansion and contraction of the piezoelectricelement 50. Note that the rocking direction D of the magnetic head 17corresponds in the seek direction (the cross track direction) of themagnetic head 17 above the magnetic disk 16.

The second bridge portion 47 d provided along the first bridge portion47 c, on which the respective piezoelectric element 50 is mounted,includes the thin portions 60. Therefore, the rigidity of the secondbridge portion 47 d is lower than those of the other portions of themultilayered member 41. Consequently, the driving force by the expansionand contraction of the piezoelectric element 50 does not easilypropagate to the second bridge portion 47 d, and thus the driving forcecan be propagated directly to the first bridge portion 47 c and thehandle 36 f. For this reason, the stroke (movement) of the piezoelectricelement 50 and the first bridge portion 47 c per unit voltage can beimproved or increased without changing the characteristics or size ofthe piezoelectric element 50. In this manner, the position of themagnetic head 17 can be controlled with higher accuracy and in a widerrange.

FIG. 8 shows the results of comparisons between various types ofsuspension assemblies based on simulations of the stroke (thedisplacement in the longitudinal direction) of the first bridge portioncaused by expansion and contraction of the piezoelectric element. InFIG. 8, case (a) indicates the stroke of the suspension assembly inwhich the base insulating layer does not include a thin portion, case(b) indicates the stroke of the suspension assembly according to thisembodiment by which the thin portion is formed in the second bridgeportion, and case (c) indicates the stroke of the suspension assembly inwhich the thin portion is formed in both the second bridge portion andthe first bridge portion. Further, FIG. 8 indicates the ratio in strokebetween the cases (a), (b) and (c) when setting the stroke of case (a)to 1.

From FIG. 8, it can be understood that the stroke of the suspensionassembly of case (b), which is the present embodiment, is increased byabout 3% as compared to the case (a). Further, when the first bridgeportion is formed to include a thin portion in addition to the secondbridge portion as in the case (c), the stroke of the suspension assemblyis decreased by 2% as compared to the case (a). This result indicatesthat the reduction in the rigidity of the second bridge portion in thecase (b) is effective for increasing the stroke. In other words, it isdesirable that the thin portion be formed only in the second bridgeportion, but in no other portions.

As described above, according to the first embodiment, it is possible toprovide a suspension assembly which can be improve the strokes withouthaving to change the characteristics or size of the drive element, sucha head suspension assembly and a magnetic disk comprising this assembly.

Next, a head suspension assembly for an HDD, according to anotherembodiment will now be described. In the embodiment described below, thesame structural elements as those of the first embodiment describedabove are designated by the same referential symbols, and the detailedexplanations therefor are omitted.

Second Embodiment

FIG. 9 is a cross section of a thin portion of a head suspensionassembly according to a second embodiment. According to the secondembodiment, in a thin portion 60 of a second bridge portion 47 d, thethickness of a cover insulating layer 44 d is set less than thethickness of the cover insulating layer 44 d in other portions(non-thinned portion) (FIG. 7C) of the multilayered member 41. Forexample, the thickness of the cover insulating layer 44 d in thenon-thinned portions is 5 μm, whereas the thickness of the coverinsulating layer 44 d in the thinned portion is 3 μm. The difference inthickness between the cover insulating layer 44 d in the non-thinnedportions shown in FIG. 7C and the cover insulating layer 44 d in thethin portion 60 shown in FIG. 9 should desirably be 1 μm or more.Therefore, the thickness T1 of the thin portion 60 is set less than thethickness T2 of the other portions (non-thinned portions) of themultilayered member 41 by 1 μm or more.

The multilayered member 41 including the above-described thin portion 60can be formed in the following process. That is, for example, afterforming the base insulating layer 44 b, the conductive layer 44 c andthe cover insulating layer 44 d are stacked on the base insulating layer44 b in this order. Then, a photoresist is formed on the coverinsulating layer 44 d, and the photoresist is exposed using a photomaskincluding a part opposing the thin portion, which has a lighttransmissivity different from that of the other parts, followed bydevelopment. Further, the cover insulating layer is etched with theobtained photoresist. Thus, the cover insulating layer 44 d includingthe thin portion 60 is formed.

In the second embodiment, the other structural parts of the HDD and thehead suspension assembly are the same as those of the HDD and the headsuspension assembly according to the first embodiment. With the secondembodiment, an advantageous effect similar to that of the firstembodiment can be obtained.

Third Embodiment

FIG. 10 is a cross section of a thin portion of a head suspensionassembly according to a third embodiment. According to the thirdembodiment, a cover insulating layer 44 d is removed from a thin portion60 of a second bridge portion 47 d. An exposed conductive layer 44 c,that is, signal traces 45 a and an upper surface of a base insulatinglayer 44 b are covered by a plating layer 45 f of nickel/Au plating orthe like, for antirust processing. The thickness of the plating layer 45f is about 0.05 μm.

With this structure, the thickness T1 of the thin portion 60 is set lessthan the thickness T2 of the other portions (non-thinned portions) ofthe multilayered member 41 by 1 μm or more, for example, about 5 μm.

In the third embodiment, the other structural parts of the HDD and thehead suspension assembly are the same as those of the HDD and the headsuspension assembly according to the first embodiment. With the thirdembodiment, an advantageous effect similar to that of the firstembodiment can be obtained.

Fourth Embodiment

FIG. 11 is a cross section of a thin portion of a head suspensionassembly according to a fourth embodiment. According to the fourthembodiment, in a thin portion 60 of a second bridge portion 47 d, thethickness of a base insulating layer 44 b is set less than the thicknessof the base insulating layer 44 b in other portions (non-thinnedportion) of the multilayered member 41. For example, the thickness ofthe base insulating layer 44 b in the non-thinned portion is 8 μm,whereas the thickness of the base insulating layer 44 b in the thinportion 60 is 4 μm, which is substantially a half thickness. Further,the thickness of the cover insulating layer 44 d in the thin portion isset less than the thickness of the cover insulating layer 44 d of theother portions (non-thinned portion) of the multilayered member 41. Forexample, the thickness of the cover insulating layer 44 d in thenon-thinned portion is 3 μm, whereas the thickness of the coverinsulating layer 44 d in the thin portion 60 is 3 μm. With thisstructure, the thickness T1 of the thin portion 60 is set less than thethickness T2 of the other portions (non-thinned portions) of themultilayered member 41 by 1 μm or more, for example, about 6 μm.

Thus, with the fourth embodiment, an advantageous effect similar to thatof the first embodiment can be obtained. Further, according to thefourth embodiment, the thickness T1 of the thin portion 60 can be lessthan that in the first embodiment, to make the rigidity of the secondbridge portion 47 d even lower. Thus, transmission of the driving forceproduced by the expansion and contraction of the drive element 50 to thesecond bridge portion 47 d can be reduced further, and the stroke of thefirst bridge portion 47 c (movement) can be increased more.

Fifth Embodiment

FIG. 12 is a cross section of a thin portion of a head suspensionassembly according to the fifth embodiment. According to the fifthembodiment, in a thin portion 60 of a second bridge portion 47 d, thethickness of a base insulating layer 44 b is set less than the thicknessof the base insulating layer 44 b in other portions (non-thinnedportion) of the multilayered member 41. For example, the thickness ofthe base insulating layer 44 b in the non-thinned portion is 8 μm,whereas the thickness of the base insulating layer 44 b in the thinportion 60 is 4 μm, which is substantially a half thickness. Further, acover insulating layer 44 d is removed from the thin portion 60 of thesecond bridge portion 47 d. An exposed conductive layer 44 c, that is,signal traces 45 a and an exposed upper surface of the base insulatinglayer 44 b are covered by a plating layer 45 f of nickel/Au plating orthe like, for antirust processing. With this structure, the thickness T1of the thin portion 60 is set less than the thickness T2 of the otherportions (non-thinned portions) of the multilayered member 41 by 1 μm ormore, for example, about 9 μm.

According to the fifth embodiment of the above-described structure, thethickness T1 of the thin portion 60 can be even less as compared to thatin the fourth embodiment. Thus, the stroke of the multilayered memberand the first bridge portion, produced by the expansion and contractionof the drive element can be further improved.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

For example, the embodiments described above have such structure that apair of drive elements 50 are attached to the gimbal portion 36 andlocated in the proximal end side of the load beam 35 with respect to themagnetic head 17, but the structure is not limited to this. A pair ofdrive elements may be arranged, for example, on both width sides of thesupport portion (tongue portion) which supports the magnetic head andmay be located in a line with the magnetic head. As to the piezoelectricelements, it is not limited to a pair, but, for example, a single driveelement may be used.

Moreover, in the disk device, the type of the magnetic disk is notlimited to 2.5 inches, but magnetic disks of other sizes may also beused. The number of magnetic disks is not limited to two, but one orthree or more disks may also be used. The number of suspensionassemblies may be decreased or increased according to the number ofmagnetic disks installed.

What is claimed is:
 1. A suspension assembly comprising: a supportplate; a trace member provided on the support plate; and anexpandable/contractable drive element mounted on the trace member, thetrace member further comprising a metal plate including an end portionfixed to the support plate, and a multilayered member on the metalplate, the multilayered member comprising a first insulating layer, aconductive layer stacked on the first insulating layer, and a secondinsulating layer stacked on the conductive layer, and including a mountportion on which the drive element is mounted, and a branching portionarranged along the mount portion with a gap therebetween, wherein thebranching portion comprises at least one portion formed into a thinportion having a thickness less than other portions of the multilayeredmember.
 2. The suspension assembly of claim 1, wherein, in the thinportion, the first insulating layer has a thickness less than that ofthe first insulating layer in other portions of the multilayered member.3. The suspension assembly of claim 2, wherein difference in thicknessbetween the first insulating layer in the thin portion and the firstinsulating layer in other portions of the multilayered member is 1 μm ormore.
 4. The suspension assembly of claim 1, wherein, in the thinportion, the second insulating layer has a thickness less than that ofthe second insulating layer in other portions of the multilayeredmember.
 5. The suspension assembly of claim 4, wherein difference inthickness between the second insulating layer in the thin portion andthe second insulating layer in other portions of the multilayered memberis 1 μm or more.
 6. The suspension assembly of claim 1, wherein, in thethin portion, the second insulating layer is removed.
 7. A headsuspension assembly comprising: the suspension assembly of claim 1, anda magnetic head provided on the trace member of the suspension assembly.8. The head suspension assembly of claim 7, wherein, in the thinportion, the first insulating layer has a thickness less than that ofthe first insulating layer in other portions of the multilayered member.9. The head suspension assembly of claim 8, wherein difference inthickness between the first insulating layer in the thin portion and thefirst insulating layer in other portions of the multilayered member is 1μm or more.
 10. The head suspension assembly of claim 7, wherein, in thethin portion, the second insulating layer has a thickness less than thatof the second insulating layer in other portions of the multilayeredmember.
 11. The head suspension assembly of claim 10, wherein differencein thickness between the second insulating layer in the thin portion andthe second insulating layer in other portions of the multilayered memberis 1 μm or more.
 12. The head suspension assembly of claim 7, wherein,in the thin portion, the second insulating layer is removed.
 13. Thehead suspension assembly of claim 7, wherein the metal plate comprises asupport portion located apart from the end portion, the mount portionforms a first bridge portion extending from the end portion to over thesupport portion, and the branching portion forms a second bridge portionextending from the end portion side and connected with a middle portionof the first bridge portion, and the conductive layer comprises aplurality of traces extending from the end portion side to a distal endportion of the first bridge portion through the second bridge portion.14. A disk device comprising: a disk recording medium; the suspensionassembly of claim 1; and a magnetic head provided on the suspensionassembly.
 15. The disk device of claim 14, wherein, in the thin portion,the first insulating layer has a thickness less than that of the firstinsulating layer in other portions of the multilayered member.
 16. Thedisk device of claim 15, wherein difference in thickness between thefirst insulating layer in the thin portion and the first insulatinglayer in other portions of the multilayered member is 1 μm or more. 17.The disk device of claim 14, wherein, in the thin portion, the secondinsulating layer has a thickness less than that of the second insulatinglayer in other portions of the multilayered member.
 18. The disk deviceof claim 17, wherein difference in thickness between the secondinsulating layer in the thin portion and the second insulating layer inother portions of the multilayered member is 1 μm or more.
 19. The diskdevice of claim 14, wherein, in the thin portion, the second insulatinglayer is removed.
 20. The disk device of claim 14, wherein the metalplate comprises a support portion located apart from the end portion,the mount portion forms a first bridge portion extending from the endportion to over the support portion, and the branching portion forms asecond bridge portion extending from the end portion side and connectedwith a middle portion of the first bridge portion, and the conductivelayer comprises a plurality of traces extending from the end portionside to a distal end portion of the first bridge portion through thesecond bridge portion.